i6 BYZANTINE CHURCHES CHAP. same spherical surface ; secondly, the hemispherical dome on pendentives ; and thirdly^ the hemispherical dome with a drum interposed between it and the pendentives. Flat external cornices on the dome are not uncommon in the later churches c of Byzantine Greece^ FIG. 8.—-THE SAUCER DOME OR DOME-VAULT, as in S. Sophia at Monemvasia.1 In Constantinople only one dome with a flat cornice can be regarded as original that of S. John in Trullo, a church which is exceptional also in other respects. The many other domes in the churches of Constantinople on high drums and with flat cornices are Turkish either in whole or in part. The high ribless domes of the Pana-chrantos3 for instance, circular in plan within and without, with square-headed windows,, plain stone sill, and flat cornice in moulded plaster3 may be regarded as typical Turkish drum-domes. As will appear in the sequels the dome over the north church of the Pantokrator and the domes of SS. Peter and Mark, the Diaconissa, and S. Theodosia, are also Turkish. 1 Annual B.S.A, xii, 1905-6. See also Schultz and Barnsley, Monastery of S. Luke at Stiris. FIG. 9.—THE DOME ON PENDENTIVES.